Alkylthio hydroquinones and mineral oil compositions thereof



ALKYLTHIO HYDROQUINONES AND MINERAL OIL COMPOSITIONS THEREOF John W. Brooks, Wenonah, N. J., assignor to Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Application March 18, 1952, Serial No. 277,300

18 Claims. (Cl. 252-481) This invention relates to alkylthio hydroquinones, to a method for their preparation and to their use as antioxidants in mineral lubricating oils.

it has been known that aromatic mercaptans, such as thiophenol, will react quite readily with quinone to form either phenylthio hydroquinone or phenylthio quinone, depending on whether the thiophenol or the quinone is used in excess in the reaction. As far as is known, however, there has been no disclosure in the art of the formation of alkylthio hydroquinones by the reaction of aliphatic mercaptans with quinone, although some text books indicate generally that mercaptans will react with benzoand naphthoquinones without precisely disclosing the products. In trying the reaction between n-butyl merw captan and quinone, however, applicant found that when an excess of quinone was employed, a mixture of monoand di-n-butylthio quinones was formed. On the other hand, when an excess of n-butyl mercaptan was used, a considerable portion of the butyl mercaptan appeared to be oxidized to the disulfide and only a very small amount of n-butylthio-hydroquinone was formed. The present invention, however, provides a method for conducting the reaction between an aliphatic mercaptan, such as n-butyl mercaptan, and quinone whereby alkylthio hydroquinones are obtained in good yield. The method of the invention is applicable even to tertiary alkyl mercaptans, which, as is well known, are more resistant to reactions involving a cleavage of the hydrogen atom from the sulfur atom than the normal and secondary alkyl mercaptans.

The principle of the invention is applicable to aliphatic mercaptans in general and particularly to those havingfrom 1 to about carbon atoms. As non-limiting examples of such mercaptans, the following may be mentioned:

(1) Primary, normal, mercaptans, such as methyl mercaptans, ethyl, propyl, butyl, pentyl, hexadecyl, octyl, decyl, dodecyl, tetradecyl and octadecyl mercaptans;

(2) Secondary mercaptans, such as S-butyl mercaptan, S-octyl mercaptan, S-dodecyl mercaptan and S-octadecyl mercaptan; and

(3) Tertiary mercaptans, such as t-butyl mercaptan, t-octyl mercaptan and t-dodecyl mercaptan.

As far as is known, there has been no disclosure in the prior art of the successful preparation of a tertiary alkylthio hydroquinone. Such compounds prepared by applicant in accordance with the method herein disclosed are, therefore, believed to be new compositions of matter.

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It is well known that mineral lubricating oils are subject to oxidative deterioration in use, particularly under the conditions of high temperature and pressure encountered by the oils in internal combustion engines and that said oils need to be fortified against such deteriorationby the addition thereto of chemical agents, called antioxidants; which are capable of inhibiting oxidation of the oil in use. The alkylthio hydroquinones of the present invention have been found to be excellent antioxidants for this purpose. The present invention, therefore, contem plates the use of these compounds in lubricating oil compositions. Accordingly, the objects of this invention inclue, first, a method for forming the alkylthio hydroquinones by the reaction of aliphatic mercaptans with quinones. Second, the preparation of a new class of alkylthio hydroquinones, i. e., the tertiary alkylthio hydroquinones. And, third, the provision of lubricating oil compositions containing alkylthio hydroquinones as antioxidants. I t

In accordance with the invention, it has been found that the alkylthio hydroquinones can be prepared in good yield by the reaction of the mercaptan with the quinone in the presence of an acidic catalyst. Suitable acid catalysts are, for example, hydrogen chloride, p-toluenesulfonic acid, sulfuric acid, phosphoric acid, trichloroacetic acid, hydrofluoric acid, etc. A Friedel-Crafts catalyst, such as FeCls, AlCla or ZnCl2, may also be used. It has been found further that the reaction proceeds best at relativelylow temperatures, i. e., from about 0 C. to about C., the higher temperatures within this range favoring the formation of the mono-substituted alkylthio hydroquinones and the lower temperatures, i. e., from about 0 C. to about 10-15 C., favoring the formation of the higher-substituted alkylthio hydroquinones, (see Examples 7 and 8, Table II). It has been found further that for the desired products to be obtained in good yield, an excess of mercaptan should'be used. Although equimolar quantities of quinone and mercaptan may be used in the reaction, it has been found that the use of at least about 2 mols of mercaptan per mol of quinone provides higher yields of the desired alkylthio hydroquinones. The reaction is generally completed in from about 3 to about 6 hours. a

The method of forming the alkylthio hydroquinones in accordance with the invention is illustrated by the results shown in Tables I and II for a number of reactions carried out between aliphatic mercaptans and hydroquinone. Table I shows the results obtained using HCl as a catalyst. All of these reactions were run under approximately the following conditions. One moi of quinone, about 3 mols of mercaptan and 1200 g. of benzenewere stirred at 5-10 C. for 3 to 4 hours while anhydrous HCl was bubbled through. The reaction mixtures were stored over night in a refrigerator and then filtered. The filtrates were washed with Water, topped to '125" C. pot temperature to remove benzene and water, and finally topped to C. pot temperature at 0.5 mm. The'product from t-dodecyl mercaptan was topped to C. at 0.5 mm. The residues (products) are mainly mixtures of mono-, diand tri-substituted alkylthio hydroquinones.

assess-i 3 4 TABLE I Reaction of alkyl mercaptans with quinone in the presence of anhydrous HCI Yield 7 Analyses Percent Sulfur Analyses Wt. Percent Hydroxyl Num- Reactants G (laid 2 (Wt. Percent) Active Hydrogen ber iflg of Fwd a c Grams (Based on Qui- Ob- Oaleu- Oh- Calcu- Ob- Calcunone) served lated served lated served laterl 108g. (1 mol) quinone; 25 65 6 54 i 300 1 270 g; (3 mols).n-but'yl m'ercaptam- 122 96 25. 2 0. 337 285 Rcddish liquid,

1,200 grbenzene 4 22-55 70 4 392 120 73 19.1 3;; e; 0. 722 391,9 is gggg hm hm liquid.

- 4 16.08 .0; 50 ,281 Light broi'vi'i liquid 105 cs 15. 2 a 12. 6 o. 73 0:80 334 442 (viscousy 19s 59 12. e 4 12. 54 o. 389 i 0. 39 320 4 220 Reddish brown l q- 1,600 g. benzene uid (very viscous). 5 '?%5g; (0.511I01) qumone. I 22.35 d

g' (1.5 mols) t-butyl mercaptan. 1.5 14 17. 46 3 16 Black tarry so 1 600 g. benzene",

Calculations are based on the assumption that the product is a mixture of the indicated substituted h'ydroquinones in the proportion indicated by the sulfur analysis. The theoretical amounts JJI substituted hydroquinones which may result trom 1 mol of quinone are: (1) 1 mol oi monosubstituted hydroquinone, (2) mol of (ii-substituted hydroquinone or (3) mol of tri-substituted hydroquinone.

B Calculations for mono-alkylthiu hydroquinones. I 4 Calculations for di-alkylthio hydroguinones; Calculations tor tri-alkyl thlo hydrqquinones.

. -,T; ib ,e,UII s mmarizes he results-obtained. by reacting the quinone, t-butyl n erciaptan he iz l i21 52 919 9 'i llfl ap l i quinone the presence of p-toluenesulfonic acid were placed in the fias k together and resulfonic acid under the conditions shown in the table, acted at 10 C, and 89? (3,, respectively for} hours @XCfiP ha xa pl s 5 and 6 weremun inthe absence of while in, Examples 9, 10 and 1,1, 'the quinone was added the catalyst. Itwill be, seen fromfIIable II that the presto a mixture of the inercapta n penzene and p-toluenesulence ot thep-toluenesulfqnic acid.catalyst vprovides markfonic acid over a period of ahoutl /a hours and thenthe edlyimproved yields of the alkylthio hydroquinonep'rodmixture was heated at C for 4 ]1 ours. This latter uct, e1ther at low temperaturei(oompare Examples 5 and procedure aflords better control of the reaction, which 7') or at the relatively .high temperatures (compare Exis exothermic and also insures e g ood excess of merample 6 with Examples 8-11). In. Examples 7 and 8, captau at all times in the course of the reaction.

TABLE II Reaction of t e r t t ri erccbtens with time in the presence of p-toluenesulfonic acid Yield Analyses inhibit I Reaction I Percent i Base of Number Ream Conditions olfialcd. Suliur ir e efiydmyl Pro uet Grams (Based (Wt. um Nut-n5 Percent Weight 54 g. (0.5 mol) ouinone. v r 5hrs.at5-10 O..- 5 gf gfm None {Overnight in is: is 14 17:46 Black tar-like a kggfi g I irigerator. mammalg. mo quinone; 511 at 0 6 g g-f Fmzm'butylme" .do {Overnightatro'oin 25 28' 18.33 Do- 22 g g% i?- -1 -1 fi1 temperature. g. .me Q one a 4hrs. at 10 O 20.79 226 373 I h 7 1 9 9 i flg ggg {over weekend in 5s 70 16.16 aies ',566}White solid.

6 K refrigerator. 22.35 286 4 392 543. (0.5 mol) quinone h v v v I s g-f g; 9 "215 4111-5 at so" c: 167 10s isles 102 "625 600 g. benzene i. j.;.- i i %t%i"- a g. mo s u y merg. p-to uene- Y 9 mm H mm mm do 32s as 16.92 19s :60 whms hd.

ggoofiblgenzelneunen; i

g. mo quinone 10 143 g (1 mol) t-octyl mer- 10 s -toi ene do 112 4 ,3? Egg 3 }Light 2 0 vis- 1 s oncac s '1 cons q 5520 gkggnzeiienn 4 f 08 4 281 1111mm 12'; 356 Refinish-brown ll 5' g t'dodecyl 0 a =10. 3152" }lie1ui d. (Very 600 g benzene 12. 220 viscous) I 1 Calculations are based on the productsbeing mixtures otmonoand iii-substituted elky fi fiydrdllulfionfi- Thiompasitidnsol H1939 mixtures are based on their sulfur analyses. The theoretical amounts of substituted hydroquinones which may result irom one mol of quinone are: '(1) 1 mol 0! monalkylthio hydroqumone and (2) 36 mol of dialkylthio hydroquiuone-i r rm,-

= The sulfur content or this productis too high. It probablly contained some unreaeted mereapt'an. H Calculations for mouo-alkylthlo hydroquino'nes. Calculations for di-alkylthio hydroquinones.

ANTIOXIDANT ACTION The products obtained in the reactions described in Tables I and II were blended with oil and the blends were subjected to a modified German tar test to determine the antioxidant properties of the compounds. This test involves heating a lSO-gram sample of the oil at a temperature of 120 C. while bubbling oxygen gas through the oil for a period of 70 hours. The acidic oxidation products formed are then determined by titrating with alcoholic potassium hydroxide. Results for the oil alone and for the oil blends are given in Table Ill in terms of neutralization numbers (N. N.), such numbers representing the acidity of the oil at the end of the test.

The base oil used in this test was a highly refined oil, suitable for use in transformers, which had been prepared by treating a coastal distillate with 40 pounds of 98% sulfuric acid and 180 pounds of 103% oleum per barrel, followed by a clay percolation. It had a specific gravity of 0.871, a flash point of 310 F.. and a Saybolt Universal Viscosity of 69 seconds at 100 F. Such an oil forms mainly acidic products on oxidation, which are indicated by a high N. N. value.

TABLE III Percent Compound Added Used Example 1 Example 2 Example Example 4. Example 7.

Example 11 These compounds were also blended with a motor oil to determine their efiect on bearing corrosion. Motor oils, especially those refined by certain solvent-extraction methods, tend to oxidize when submitted to high temperatures and form products that are corrosive to metal bearings. This corrosive action may be quite severe with certain bearings, such as those having the corrosion susceptibility of cadmium-silver alloys; and it may cause their failure within a comparatively short time. The following test was used to determine the corrosive action of a motor oil on an automobile connecting-rod bearing.

The oil used consisted of Pennsylvania neutral and residuum stocks separately refined by means of Chlorex,

and then blended to give an SAE motor oil with a d specific gravity of 0.872, a flash point of 435 F, and a Saybolt Universal Viscosity of 318 seconds at 100 F. The oil was tested by immersing therein about a G-gram section of a bearing containing a cadmium-silver alloy surface and heating it to 175 C. for 22 hours while a stream or" air was bubbled against the surface of the bearing at the rate of two liters per hour. The loss in weight of the bearing during this treatment measures the amount of corrosion that has taken place. The results obtained from this test are given in Table IV.

Several of the product compounds were also subjected to the Lauson Oxidation Stability Test, the purposeof which is to determine oil deterioration as primarily indicated by corrosion of copper-lead bearings. The oil employed for this test consisted of Pennsylvania neutral and residuum stocks separately refined bymeans .of Chlorex and then blended to give an SAE 10 motor'oil. A Lauson single cylinder, 4-cycle, liquid cooled gasoline engine with splash lubrication using copper-lead bearings was operated under the following conditions.

The bearing corrosion results after one hundred hours of operation are shown in Table V.

TABLE V Bearing Wt. Loss (G.) Av. of Top and Bottom Ooncn. (Wt. Percent) Compound Added Example 2. Example 3.

Example 4 From the foregoing test results, it can be observed that the reaction products contemplated herein are highly efiective for stabilizing viscous petroleum oil fractions against the normal deteriorating eifects of oxidation.

The alkylthio hydroquinones of the invention may be used in the lubricating oil in amounts ranging from about 0.01 per cent up to about 10 per cent, depending upon the particular oil and the amount of improvement desired. For most purposes, however, the use of from about 0.1 to about 2 per cent of the additive is sufficient to provide the desired improvement.

The products herein described may be used in lubricating oils in combination with other addition agents designed to impart different improving properties to the oil, such as detergents, V. I. improvers, pour point depressants, antifoam agents, antirust agents, extreme pressure agents, etc.

Although the invention has been illustrated herein by means of certain specific examples, it is not intended that the scope of the invention be limited thereby, but only as indicated in the following claims.

What is claimed is:

l. A method for preparing an alkylthio-substituted hydroquinone which comprises reacting 1 mol of quinone with at least 1 mol of an aliphatic mercaptan in the presence of an acidic catalyst at a temperature of from about 0 C. to about C. and for a time period of at least about 4 hours.

2. A method for preparing an alkylthio-substituted hydroquinone which comprises reacting 1 mol of quinone with at least 1 mol of an aliphatic mercaptan in the presence of hydrogen chloride at a temperature of from about 0 C. to about 100 C. and for a time period of at least about 4 hours.

3. A method for preparing an alkylthio-substituted hy droquinone which comprises reacting 1 mol of quinone with at least 1 mol of an aliphatic mercaptan in the presence of p-toluene sulfonic acid at a temperature of from about 0 C. to about 100 C. and for a time period of at least about 4 hours.

4. A method for preparing n-butylthio-substituted hydroquinone which comprises reacting 1 mol of quinone with at least about 2 mols of butyl mercaptan in the presence of a paratoluene sulfonic acid at a temperature of from about 0 C. to about 100 C. and for a time period of at least about 4 hours.

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5. A method for-preparing a t alkylthio substituted hydroquinone which comprises reacting '1 mol ofs'qu'inone with tit-least about 2 mols of a tertiaryaliphatic mercaptan inthe presence of paratoluene sultonic acid ata temperature-of from aboutfi" C.to about 100C. and for a time periodof atfleast about 4 hours.

6. Ameth'od r'or preparing a t buty1thio=substituted hydroquinone which comprises reacting 1 :mol :of :quinone with at least about '2 molsof tertiary butyl mercap'tan in the presence of p-toluene sulfonic acid at a temperature of from about C. to about 100 C. and for a time period of at least about 4 hours.

7. A method for preparing t-octylthio-ssubstituted hydroquinone which comprises reacting 1 .mol of .quinone with at least about 2 mols of tt-octyl mercaptan -in the presence of p-toluene sulfonic acid at a temperature of from about 0 'C. to about 100 C. and for a time period of at least 4 hours.

8. A method for preparing tertiary dodecylthio-substituted hydroquinone which comprises reacting 1 mol of quinone with at least about 2 mols of tertiary dodecyl mercaptan in the presence of paratoluene sulfonic acid at a temperature of from about 0 C. to about 100 C. and for a timeperiod of at least about 4 hours.

9. As a new composition of matter, a tertiary alkylthiosubstituted hydroqu'inone.

":10. As a new composition of matter, a -t-butylthio substituted'hydroquinone.

11. As a new composition of matter, a t-octylthiosubstituted hydroquinone.

12. As a new composition of matter, a.t-dodecylthiosubstituted hydroquinone.

13. A mineral lubricating oil containing a minor pro portion, sufiicient to inhibit said oil against oxidation, .of an aikylthio-substituted .hydroquinone.

14. A mineral lubricating oil containing a minor proportion, ,sufiicient ;to inhibit said oil against oxidation, of a n-butylthio-substi-tuted hydroquinone.

15. A mineral lubricating oil containing a minor proportion, .suflicient to inhibit said oil against oxidation, of a tertiary aikylthio-substituted hydroquinone.

16. A mineral lubricating .oil containing a minor proportion, ,sufficient to inhibit said (oil against oxidation, of a t-butylthio-substituted hydroquinone.

17. A mineral lubricating oil containing a minor proportion, sufiicient .to inhibit/said oil against oxidation, of a t-octylthio-substituted hydroquinone.

.18. A mineral lubricating oil containing a minor proportion, sufficient to inhibit said oil against oxidation, of a t-dodecylthio-substituted hydroquinone.

References Cited in the file of this patent UNITED STATES PATENTS Newby Apr. 17, 1951 Ladd et al May 15, 1951 

1. A METHOD FOR PREPARING AN ALKYLTHIO-SUBSTITUTED HYDROQUINONE WHICH COMPRISES REACTING 1 MOL OF QUINONE WITH AT LEAST 1 MOL OF AN ALIPHATIC MERCAPTAN IN THE PRESENCE OF AN ACIDIC CATALYST AT A TEMPERATURE OF FROM ABOUT 0* F. TO ABOUT 100* C. AND FOR A TIME PERIOD OF AT LEAST ABOUT 4 HOURS.
 10. AS A NEW COMPOSITION OF MATTE, A T-BUTYLTHIOSUBSTITUTED HYDROQUINONE. 